According to research published in 2002 in the "Journal of Infectious Diseases," about two-thirds of Americans eventually acquire the herpes simplex virus that causes fever blisters. While prescription antiviral drugs work well, doctors usually reserve them for patients with severe, prolonged or recurrent fever blisters. The Food and Drug Administration allows just one over-the-counter medication, topical docosanol, to claim effectiveness in reducing the severity and duration of fever blisters.

Indications

The Food and Drug Administration has approved docosanol for use on recurrent episodes of fever blisters. Docosanol comes in a standard 10 percent strength white cream that dries with a clear finish. You apply docosanol five times per day until lesions heal. However, docosanol does not work on fever blisters inside the mouth or nose. Pregnant women and children younger than 12 should not use docosanol, except as recommended by a doctor.

Effectiveness

Docosanol works by preventing the virus that causes fever blisters from entering skin cells. According to the textbook "Basic and Clinical Pharmacology" published in 2008, clinical studies show that docosanol accelerates healing of recurrent fever blisters by about 18 hours and offers interim relief from pain or itching. Docosanol does not destroy the herpes simplex virus or reduce the likelihood of fever blister recurrence. For maximum effectiveness, you should begin applying docosanol when you experience early symptoms of fever blisters, such as tingling, itching or burning.

Side Effects and Complications

Docosanol is a common ingredient in cosmetics and personal care products, so it is generally safe and well-tolerated. The most common side effect of docosanol is headaches. A smaller number of people experience acne, burning, dryness, itching, redness, rash, soreness or swelling. If you experience severe side effects, you should discontinue use and contact your doctor for further instructions. Fever and pus or thick, white exudate suggests that the fever blister has become infected with bacteria. Washing hands before applying docosanol can reduce the risk of this complication. If you notice signs of infection, you should contact your doctor without delay.